Okay, so really this is the same thing as being this:\[(b-3)\div-5=-15\]Now, like I said before - you have to work backwards. Do PEMDAS backwards. SADMEP. So if you do it correctly, it would come out b=78

This is what I thought:
13 = -8p - 3 + 9p
I combine the like terms, which are -8p and 9p by adding 9 to -8 (because you always keep the sign before the number with the number), making the equation 13 = 1p - 3.
From there I go to (13 + 3) / 1
Then 16 / 1
And 16 = p